"secret" is countable. You can have more than one, right?
EX: It is a secret. ("It" is singular)
EX: Keep it a secret. ("it" is singular)
EX: I've got a few secrets, whereas my friends has many secrets. (plural)
"advice" requires a quantifier; e.g., piece of.
EX: Could you give me some advice?
Student or Learner